Organic electro luminescent display and method for fabricating the same

ABSTRACT

An organic electro luminescent display with auxiliary layers on a cathode contact and an encapsulating junction region to easily remove polymer organic layers of the junction and a method for fabricating the same. The organic electro luminescent display has the first electrode formed on a lower insulating substrate, a pixel defining layer formed to make some portions of the first electrode opened over the entire surface of the lower insulating substrate, an organic emission layer formed on an opening of the first electrode, the second electrode formed on the organic emission layer, an upper substrate for encapsulating the first electrode, the organic emission layer and the second electrode, and auxiliary layers formed on the cathode contact and the encapsulating junction region of the lower insulating substrate.

CLAIM OF PRIORITY

This application claims priority to an application entitled “ORGANICELECTRO LUMINESCENCE DISPLAY AND METHOD FOR FABRICATING THE SAME”, filedin the Korean Intellectual Property Office on 10 Jun. 2003 and assignedSerial No. 2003-37244, and filed on 23 Jun. 2003 and assigned Serial No.2003-40808, and filed on 2 Sep. 2003 and assigned Serial No. 2003-61163,the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an organic electro luminescent display and amethod for fabricating the same and, more particularly, to an organicelectro luminescent display having an auxiliary layer encapsulatingjunction region and a method for fabricating the same.

2. Description of the Related Art

Generally, an organic electro luminescent display is an emissive displaycapable of emitting light by electrically exciting a fluorescent orphosphorescent organic compound, and phosphorescent organic compound canbe driven by a low voltage and has a thin form-factor, a wide viewingangle and a fast response speed, so that the electro luminescent displaycan solve problems that have been found in liquid crystal displays.Therefore, the electro luminescent display has attracted attention as anext-generation display.

Such an organic electro luminescent display has a structure that has anorganic light emitting diode (OLED) including an organic layer having atleast emission layer (EML), an anode, and a cathode, wherein the organiclayer having a predetermined pattern is formed on a glass or othertransparent insulating substrate, and the anode and cathode electrodesare formed on upper and lower portions of the organic layer for applyinga driving voltage to the organic layer. The organic layer consists oforganic compounds.

In the organic electro luminescent display having the above-mentionedbasic structure, as an anode electrode and a cathode electrode voltagesare applied to the electrodes, holes injected from the electrode thathave been applied with the anode electrode voltage are transported tothe emission layer (EML) through a hole transporting layer (HTL), andelectrons are injected from the electrode that have been applied withthe cathode electrode voltage are transported to the emission layer(EML) through an electron transporting layer (ETL). The electrons andholes are then recombined in the emission layer (EML) to createexcitons, and the exitons are then changed from an exciting state to aground state, thereby emitting an organic substance of the emissionlayer (EML) and embodying a required image.

In the above-mentioned organic electro luminescent display, when apolymer material is used for the organic layer, the organic layer isgenerally formed on a substrate by spin coating. However, when theorganic layer is formed by the spin coating, the organic layer is alsoformed in regions other than the pixel portion. Thus, the organic layerof the encapsulating junction region needs to be removed to encapsulatean inner structure of the organic electro luminescent display.

In a prior art, a cleaning process using an organic solvent wasperformed to remove the organic layer of the encapsulating junctionregion, however, the process has a significantly low accuracy and theorganic solvent often penetrates into the pixel portion, so that thereis a high possibility of damaging the pixel portion.

To solve the above-mentioned problems, a method using a laser isdisclosed to remove a foreign substance including organic emissivematerials off a substrate. According to a Korean laid-open PatentApplication No. 2000-0036020, a method for removing the foreignsubstance using the laser is disclosed. This method removes organic orinorganic foreign substances on the substrate by directly irradiatingthe ultraviolet laser on the surface of the substrate.

In the case of the substrate of the prior art, a metal wiring and apassivation layer are usually deposited on a glass substrate in theencapsulating junction region. However, the laser energy absorption rateof the passivation layer is small so that the organic layer is noteasily removed by using a laser.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide for animproved design for an electro luminescent display.

It is also an object of the present invention to provide for a novelmethod for making an electro luminescent display.

It is further an object of the present invention to provide for a novelstructure of an electro luminescent display that allows for easierselective removal of an organic emissive layer using a laser.

It is yet another object of the present invention to provide a novelmethod of making an electro luminescent display that more efficientlyselectively removes unwanted materials using a laser without destroyingother portions of the electro luminescent display.

It is further an object of the present invention to provide a novelstructure for an electro luminescent display that allows for sealant tobe efficiently cured by ultraviolet light while preventing other partsof the electro luminescent display from being harmed by the curingultraviolet light.

It is further an object of the present invention to provide a novelmethod for making an electro luminescent display that allows for sealantbetween the substrates and between the electrodes to be efficientlysealed by ultraviolet light where other portions of the display are notharmed by exposure to the curing ultraviolet light.

These and other objects can be achieved by an organic electroluminescent display, which has the first electrode formed on a lowerinsulating substrate, a pixel defining layer formed to make someportions of the anode electrode opened over the entire surface of thelower insulating substrate, an organic layer formed on an opening of theanode electrode, the second electrode formed on the organic layer, anupper substrate for encapsulating the anode electrode, the organic layerand the cathode electrode, and auxiliary layers formed on a cathodecontact and an encapsulating junction region of the lower insulatingsubstrate. The organic layer is deposited over the first electrode andthe auxiliary layers. The organic layer is selectively removed by laserfrom the auxiliary layers. The material for the auxiliary layers arecarefully chosen so that the organic layers can be removed from theauxiliary layers with relatively little amount of laser light.

The present invention also includes a method for making the electroluminescent display having the auxiliary layers and the application oflaser light to remove the organic layers off the auxiliary layers vialaser ablation.

The invention separately provides a novel structure for an organicelectro luminescent display. The novel display is made up of upper andlower substrates bounded to each other by an ultraviolet light curablesealant. The sealant is placed around the pixel region in anencapsulation region. A reflecting plate is placed adjacent to thesealant. The reflecting plate is used to reflect the ultraviolet lightso that less light is needed to cure the sealant. Less light or moreefficient use of the ultraviolet light means that the other parts of theelectro luminescent display are not degraded or damaged due to exposureto an excessive amount of ultra violet light. The sealant and thereflecting plate can be used in either active or passive matrix pixelstructures. In place of the reflecting plate, a waveguide can be usedadjacent to the sealant.

The present invention also pertains to a method of making the abovestructure for an electro luminescent display including the applicationof the reflective plate and/or waveguide and the ultraviolet curingstep.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or similar components, wherein:

FIG. 1 is a graph illustrating empirically a relationship betweenapplication of laser energy versus removal of an organic layer absentthe use of auxiliary layers under the organic layer;

FIG. 2 is a plane view for explaining an organic electro luminescentdisplay;

FIG. 3 is a plane view showing an organic electro luminescent displayaccording to the first three embodiments of the present invention;

FIGS. 4A to 4D are cross-sectional views illustrating the process ofmaking the display of FIG. 3 according to a first embodiment of thepresent invention;

FIG. 5 is a graph illustrating empirically a relationship betweenapplication of laser energy versus removal of an organic layer when theorganic layer is formed over the auxiliary layers according to thepresent invention;

FIG. 6A is an exploded perspective view showing an organic electroluminescent display according to a fourth embodiment of the invention;

FIG. 6B is a cross-sectional view of the display of FIG. 6A taken alongthe I-I′;

FIG. 7 is a view illustrating both a pixel region for an active matrixpixel and an encapsulating junction region according to the fourthembodiment of the invention;

FIG. 8 is a cross sectional view of the encapsulation junction regionaccording to the fourth embodiment of the present invention where areflection plate is on an inside side of the lower insulating substrate;

FIGS. 9 and 10 are plane views for explaining an arrangement of areflection plate vis-a-vis the sealant and the pixel region according tothe fourth embodiment of the present invention;

FIG. 11 illustrates a cross section of an encapsulation junction regionaccording to a fifth embodiment of the present invention where thereflection plate is on an inside side of the upper substrate;

FIG. 12 illustrates a cross section of an encapsulation junction regionaccording to a sixth embodiment of the present invention where thereflection plate is on an outside side of the lower insulatingsubstrate;

FIG. 13 illustrates a cross section of an encapsulation junction regionaccording to a seventh embodiment of the present invention where thereflection plate is on an outside side of the upper substrate;

FIGS. 14A and 14B illustrate a cross section of an encapsulationjunction region according to an eighth embodiment of the presentinvention where a wave guide is located on an inside side of the lowerinsulating substrate;

FIGS. 15A and 15B illustrate a cross section of an encapsulationjunction region according to a ninth embodiment of the present inventionwhere a wave guide is located on an inside side of the upper substrate;and

FIGS. 16A and 16B illustrate a cross section of an encapsulationjunction region according to a tenth embodiment of the present inventionwhere there are two wave guides present, one on an inner surface of theupper substrate and another on the inner surface of the lower insulatingsubstrate.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to FIG. 1, FIG. 1 illustrates empirical results forthickness of removed foreign substance based on number of laser pulsesapplied and the energy of each pulse. As illustrated in FIG. 1, as thenumber of laser pulses increases, the amount or thickness of removedforeign substances does not increase in a linear fashion with the numberof laser pulses applied. For example, as the thickness of the remainingorganic layers becomes thinner, the removal rate per additional laserpulse decreases, so that a significant amount of energy and a largenumber of laser pulses are required to completely remove the residualsubstances. Because a large number of laser pulses at a high energy perpulse is needed to completely remove the foreign substance, the lasermay cause damage to the substrate in the foreign substance removalprocess.

In addition to the removal of foreign substances by a laser, in theorganic electro luminescent display of the prior art, a sealant is usedto join the substrates together. An upper substrate is bound to a lowerinsulating substrate via this sealant. The sealant also serves toencapsulate organic electro luminescent elements and plays a role indetermining a lifetime, efficiency, etc. of the organic electroluminescent elements.

The organic electro luminescent element mainly is divided into an innerpixel portion that actually emits light and a pad portion for connectingan external driving IC for driving the pixel portion, wherein thedriving portion and the pad portion are connected by a wiring made ofopaque metals to minimize resistance. In this case, an encapsulatingprocess using a sealant is performed to prevent moisture and air from anoutside of a display from coming into contact with and destroying theorganic electro luminescent element. The sealant is ordinarily cured byexposure to light, especially ultraviolet light. However, when the lowerinsulating substrate is attached to and encapsulated by the uppersubstrate using the ultraviolet cured sealant, it takes more time tocure the sealant using the ultraviolet light. Because an immense amountof ultraviolet light is needed to cure the sealant, the ultravioletlight can damage other portions of the display, either by heating partsup or causing an unwanted chemical reaction in the display. If theamount of ultraviolet light used to cure the sealant is reduced toprevent the damage to other parts of the display, the sealant will notbe fully cured because the sealant has not received adequate exposure tothe ultraviolet light to fully cure.

Turning now to FIG. 2, FIG. 2 illustrates an organic electro luminescentdisplay of the prior art (FIG. 5 of Korean laid-open Patent ApplicationNo. 2000-0036020). The process used to form the display of FIG. 2 willnow be described. A plurality of first electrodes 3 made of opticallytransmissive materials are formed in an arbitrary pattern, such as astripe pattern, over one surface of a lower insulating substrate 1.Lower insulating substrate 1 is made out of a material that is bothelectrically insulating and optically transmissive. An insulating layer5 is formed on the first electrodes 3, and a plurality of secondelectrodes 7 are formed on insulating layer 5 in a stripe pattern to adirection orthogonal to the first electrodes 3.

In this case, pixel portions of the organic electro luminescent displayare where the first electrodes 3 and the second electrodes 7 are crosseach other. Where second electrodes 7 and first electrodes 3 cross eachother, the insulating layer 5 in these crossed regions is not present.Instead, a thin organic layers disposed in these cross over regions. Theorganic emissive material (not illustrated in FIG. 2) is also inelectrical contact with both the first electrodes 3 and the secondelectrodes 7 in the cross over areas.

In this case, an upper substrate 9 (illustrated as a dotted line in FIG.2) is disposed over a lower substrate 1, and the lower substrate 1 andthe upper substrate 9 are bound to each other by a sealant that is notillustrated in FIG. 2, so that the organic electro luminescent displayof FIG. 2 is formed.

According to the above-mentioned structure of FIG. 2, some portions ofthe first electrodes 3 and the second electrodes 7 are exposed outsidethe substrates 1 and 9 so that electrodes 3 and 7 can be electricallyconnected to circuit driving elements, for example FPC (Flexible PrintedCircuit, 11). Circuit 11 is electrically connects external equipment tothe organic electro luminescent display by thermal compression, etc.

However, in the organic electro luminescent display having theabove-mentioned structure, the process of applying and curing thesealant is not properly performed when the lower substrate 1 and theupper substrate 9 are sealed together, thereby decreasing the lifetimeand reliability of the product. In the typical prior art, a sealingmaterial is applied along the periphery of the lower substrate 1 asdescribed above and the upper substrate 9 is mounted thereon, andultraviolet rays are irradiated from the rear surface of the lowersubstrate 1 and the sealing material is cured, so that the lowersubstrate 1 and the upper substrate 9 are bonded together.

When the ultraviolet rays irradiate the sealing material disposed in aportion of the display that is exposed outside the first and secondelectrodes 3 and 7 on the substrates 1 and 9 (i.e.,the lower and rightsides of FIG. 2), the sealing material was cured without any significantproblems because the ultraviolet light was not blocked or hindered bythe electrode layers 3 and 7. However, when the ultraviolet raysirradiate the sealing material disposed in a portion of the displaywhere the striped patterns of electrode layers 3 and 7 are present(i.e., the upper and the left sides in FIG. 2) the presence of theelectrode layers 3 and 7 hinders the ultraviolet rays from effectivelyreaching the sealant between the substrates 1 and 9 thus requiring morepulses and/or higher energy pulses to fully cure the sealant in theseregions of the display. If the sealant is not properly cured by anadequate exposure to ultraviolet light, air and moisture will then beallowed to penetrate through the sealant and into the emissive layers tocause deterioration of a display.

The present invention has 10 embodiments. The first three embodimentsconcentrate on the auxiliary layers in both structure and in method ofmaking. Organic layers on top of the auxiliary layers are more easilyremoved via exposure to a laser than if the auxiliary layers were notpresent.

First Embodiment

Turning now to FIG. 3, FIG. 3 is a plane view illustrating an organicelectro luminescent display according to a first embodiment of thepresent invention, and FIGS. 4A to 4D are cross-sectional viewsillustrating a process for making the organic electro luminescentdisplay of FIG. 3 according to an embodiment of the present invention.

Referring to FIG. 4A, a first electrode (or anode electrode) 110 isdeposited on substrate (or lower substrate) 100. First electrode is madeout of a transparent and conductive material such as ITO (indium tinoxide), IZO (indium zinc oxide) or ICO (indium cesium oxide). Thistransparent first electrode material is deposited and patterned on thelower insulating substrate 100, and a transparent anode electrode, inother words, the first electrode 110 formed in the pixel portion. Lowersubstrate 100 may be a transparent substrate made out of an electricallyinsulating material, such as glass.

In the first embodiment, the auxiliary layers 120 and 130 are made outof the same material as the first electrode 110. Therefore, theauxiliary layers 120 and 130 are deposited and patterned on lowersubstrate 100 at the same time as when the first electrode 110 isdeposited and patterned on lower substrate 100. Auxiliary layer 120 isformed at cathode contact A while auxiliary layer 130 is formed atencapsulating junction region B.

After forming the auxiliary layer 130 on the encapsulating junctionregion B, the auxiliary layer 120 on the cathode contact A, and theanode 110 of the pixel portion, a pixel defining layer 140 is depositedand patterned on first electrode 110 covering parts of first electrode110 and leaving other parts of the top surface of first electrodeexposed. The pixel defining layer 140 is preferably an inorganicmaterial and a polymer such as an acrylic photoresist or a polyimide.

Next, the organic layer 150 is deposited to cover the pixel defininglayer 140, the exposed portions of the first electrode 110, theauxiliary layers 120 and 130, and over exposed portions of lowersubstrate 100. The organic layer 150 is preferably formed by spincoating. The organic emission layer 150 preferably includes at least anemission layer(EML) and has a multi-layered structure made up of atleast one of a hole injection layer (HIL), a hole transporting layer(HTL), an emission layer (EML), an electron transporting layer (ETL),and an electron injection layer (EIL).

Referring now to FIG. 4B, after forming the organic layer 150, theorganic layers on the auxiliary layers 120 and 130 over cathode contactA and the encapsulating junction region B of the substrate are removed.The process of selectively removing the organic layers 150 from theauxiliary layers 120 and 130 is preferably accomplished by exposingthese portions of organic layers 150 with light pulses from a laser.This process of removing the organic layers 150 using a laser is calledlaser ablation. In addition, a type of the laser can be selected from anUV based one (Eximer laser, Nd: YAG laser, etc) to an IR based one (Nd:YAG, CO₂ laser, etc) according to a material of a light source.

After removing the organic layers from the tops of the auxiliary layers120 and 130, a conductive material is then deposited and patterned onthe structure to form the second electrode or cathode electrode 160. Thecathode electrode 160 performs a role of transporting electrons to theelectron transporting layer of organic layer 150 by using a metalelectrode such as Al, Mg, Ag, Ca that has a low work function.

Referring now to FIGS. 4C and 4D, after forming the cathode electrode160, an upper substrate 180 is attached to the top of the electroluminescent display using an encapsulating adhesive 170. Theencapsulating adhesive is formed over auxiliary layer 130 which is overencapsulating junction region B of lower substrate 100. Therefore,encapsulating adhesive 170 is formed around the periphery of the electroluminescent display and surrounds the pixel region.

Referring to FIG. 5, FIG. 5 is a graph illustrating empirically theamount of an organic layer 150 that is removed by a laser based on thenumber of laser pulses and the energy intensity of each pulse. FIG. 5 isfor the scenario of where the organic layers 150 is supported byauxiliary layers 120 and 130. FIG. 5 is to be compared with FIG. 1 whichillustrates removal thicknesses of the organic layers when the organiclayers 150 are not on top of an auxiliary layer. In the method forremoving foreign substances on the substrate 100 where the foreignsubstances are organic layers on top of an auxiliary layer 120/130, byusing the auxiliary layers 120 and 130, the organic layers are moreeasily removed since less pulses and less intensity is needed to removethe organic layers when they are supported by auxiliary layers 120 and130. It is to be appreciated that other materials can also be removed bythe laser in addition to the organic layers. Therefore, in thisspecification, foreign substances includes the organic layers but is notlimited thereto. Less number of pulses and less intensity of pulsesmeans that the remainder of the electro luminescent display sustainsless damage from the laser pulses when auxiliary layers 120 and 130 areused (FIG. 5) compared to when they are not used (FIG. 1).

FIG. 5 illustrates that 12 pulses with an energy intensity of 75 J/cm²can remove the entire organic layer if the organic layer is supported byauxiliary layers 120 and 130. This compares with 25 pulses of 100 J/cm2for when the organic layers are not supported by the auxiliary layers.Because having the auxiliary layers 120 and 130 present allows for theremoval of the organic layers with less pulses with less intensity, theother parts of the electro luminescent display sustain less damage whenauxiliary layers 120 and 130 are incorporated into the design.

More preferably, a removing depth of the organic layer can be maximizedby irradiating the laser with energy density not less than 125 mJ/cm².That is, when the organic layers are removed by using the auxiliarylayer and the laser, energy required for removing the organic layers issmall.

Second Embodiment

The organic electro luminescent display according to a second embodimenthas a similar structure as that of the first embodiment except thematerial used for the auxiliary layers 120 and 130 is different. In thesecond embodiment, the material used in the auxiliary layers 120 and 130is the same as the material used in pixel defining layer 140. Therefore,pixel defining layer 140 and the auxiliary layers 120 and 130 can beformed at the same time. The pixel defining layer and the auxiliarylayers are deposited at the same time and the patterning and etching ofthe pixel defining layer 140 and auxiliary layers 120 and 130 areaccomplished in a single step. As discussed previously, the pixeldefining layer 140 is preferably an inorganic material and a polymersuch as an acrylic photoresist or a polyimide. By having the auxiliarylayers 120 and 130 made out of the same material as the pixel defininglayer 140, the number of pulses needed and the energy intensity of eachpulse to remove the organic layer is reduced from the case of FIG. 1where no auxiliary layers were present.

Third Embodiment

The organic electro luminescent display according to a third embodimenthas a similar structure as that of the first embodiment except that theauxiliary layers 120 and 130 for removing the organic layers 150 areformed by using materials having a laser energy absorption rate higherthan that of the organic layer 150 for the laser wavelength used toremove the organic layer.

That is, after forming the pixel defining layer 140 in the firstembodiment, the auxiliary layers 120 and 130 are formed on the cathodecontact A and the encapsulating junction region B by depositing andpatterning materials having a higher laser energy absorption rate forthe laser wavelength used in the removal process

The third embodiment is not necessarily mutually exclusive from thefirst or the second embodiment. For example, use of ITO, IZO or ICOcould result in the auxiliary layer having a higher absorption of thelaser light than the organic layer and thus the auxiliary layers 120 and130 can still be made at the same time as the first electrode 110. Also,use of acrylic photoresist or polyimide for auxiliary layers 120 and 130may have a higher absorption than organic emission layer 150 and thusthe auxiliary layers 120 and 130 can be made at the same time that thepixel defining layer 140 is made.

Now embodiments 4 through 10 will now be discussed. In theseembodiments, the focus is on an ultraviolet cured sealant used to fix atop substrate to the bottom substrate. A reflecting plate and/or a waveguide is placed adjacent to the sealant so that the sealant can be curedwith less ultraviolet light than if no reflecting plate or waveguide isused. Consequently, by using less ultraviolet light to cure, theremaining parts of the electro luminescent display are subjected to lessultraviolet radiation and thus less damage results.

Fourth Embodiment

Turning now to FIGS. 6A and 6B, FIG. 6A is an exploded perspective viewillustrating an organic electro luminescent display according to afourth embodiment of the invention, and FIG. 6B is a cross-sectionalview taken along the I-I′ direction of FIG. 6A. Referring to FIGS. 6Aand 6B, the organic electro luminescent display of the fourth embodimentof the present invention has a structure that a lower insulatingsubstrate 200 having a pixel portion is bonded to an upper substrate 320at an encapsulating junction region, the plurality of pixels beinglocated in the pixel portion. That is, in the organic electroluminescent display of the present invention, the pixel portion isformed on the upper side of the transparent lower insulating substrate200, and can be formed in a typical structure of the organic electroluminescent display. The fourth embodiment can be either a passivematrix or an active matrix using thin film transistors or TFTs.

For example, when the organic electro luminescent display L is formed ina passive matrix (PM) type, the pixel portion is made up of electrodelayers corresponding anode and cathode electrodes, respectively, andorganic layers having emission layer disposed on positions correspondingto the common portions where the anode and cathode layers cross eachother. When the organic electro luminescent display is formed in aactive matrix (AM) type, the pixel portion can further include thin filmtransistors TFTs. The fourth embodiment of the present invention can beapplied to any structure with the pixel portion, however, for example,an active matrix organic electro luminescent display will now bedescribed in conjunction with FIG. 7.

Turning now to FIG. 7, FIG. 7 illustrates a cross-sectional viewillustrating an active matrix type pixel and an encapsulating junctionregion according to the fourth embodiment of the present invention. FIG.8 is a cross-sectional view illustrating an encapsulating junctionregion of the organic electro luminescent display according to thefourth embodiment of the invention. The organic electro luminescentdisplay according to the fourth embodiment of the present invention hasa structure that includes a reflecting plate 267 adjacent to sealant330. Reflecting plate 267 and sealant 330 are disposed in theencapsulation portion region of the electro luminescent display. Sealant330 permanently binds the upper substrate 320 to the lower substrate200.

Referring to FIGS. 7 and 8, a method for fabricating the organic electroluminescent display having the reflecting plate 267 in the encapsulatingjunction region will now be described. Referring to FIG. 7, a bufferlayer 210 is formed on the lower insulating substrate 200 to preventimpurities such as metal ions diffused from the lower insulatingsubstrate 200 from penetrating to an active layer. After forming thebuffer layer 210, amorphous silicon is deposited and crystallized on thebuffer layer 210 to form a polycrystalline silicon layer, which is thenpatterned to form the active layer 220. A gate insulating layer 230 isdeposited on all surfaces of the lower insulating substrate 200containing the active layer, and gate metal is deposited and patternedon the gate insulating layer to form a gate electrode 240.

After forming the gate electrode 240, an impurity having a predeterminedconductive type is doped in the active layer by using the gate electrode240 as a mask to form source/drain regions 221 and 225. A region with noimpurity doped between the source region 221 and the drain region 225acts as a channel region 223. After forming the source/drain regions 221and 225 on the active layer 220, an interlayer insulating layer 250 isformed over the entire surface of the lower insulating substrate 200,and contact holes 251 and 255 are formed to expose some portions of thesource/drain regions 221 and 225 on the interlayer insulating layer 250.

After depositing a conductive material on the interlayer insulatinglayer 250 including the contact holes 251 and 255, the conductivematerial is patterned to form source/drain electrodes 261 and 265connected to the source/drain regions 221 and 225 through the contactholes, thereby forming a TFT (T) consisted of the active layer 220, agate electrode 240, and the source/drain electrodes 261 and 265, etc.

In this case, when the source/drain electrodes 261 and 265 are formed, areflecting plate 267 of a metal thin layer consisted of the conductivematerial is also formed in the encapsulating junction region of thelower insulating substrate 200 at the same time. A metal having a goodreflectivity is used for the conductive material, and generally Al, Cr,Mo, W, Ti, Ta, or alloy thereof is used for the same. After forming thereflecting plate 267 of the encapsulating junction region and thesource/drain electrodes 261 and 265, a passivation layer 270 isdeposited on the lower insulating substrate 200, and a via-hole 275 isformed on the passivation layer 270 to expose some portions of one ofthe source electrode 261 and the drain electrode 265, for example, someportions of the drain electrode 265.

After depositing a lower electrode material on the passivation layer 270including the via-hole 275, the lower electrode is patterned to form alower electrode 280 electrically connected to the drain electrode 265through the via-hole 275. After forming the lower electrode 280, a pixeldefining layer 290 is deposited on the entire surface of the lowerinsulating substrate 200 and patterned to form an opening portion 295that exposes some portions of the lower electrode 280.

An organic layer 300 is then formed on the pixel defined layer 290including the opening portion 295. And an upper electrode 310 is formedon the organic layer 300 over the entire surface of the lower insulatingsubstrate 200 to form a light emitting element (LE) made up of the lowerelectrode 280, organic layer 300, and the upper electrode 310. The lowerinsulating substrate 200 is then encapsulated to the upper substrate 320by using a sealant 330 in the encapsulating junction region.

The sealant 330 is preferably a light-curing sealant, and morepreferably a light curing sealant capable of being cured not only byexposure to light in an ultraviolet range but also to light in thevisible range. 30Y-296G (three bond), XNR5516 (Nagase Ciba),electrolyte, or Kyoritsu are preferably used for the sealant 330.

In addition, the thickness “L” in FIG. 8 of the sealant 330 is adistance between the reflecting plate 267 and the upper substrate 320.This thickness L is preferably set to cause constructive interference inthe light used to cure the sealant 330. Constructive interference is tooccur between the incident light and the light reflected off thereflecting plate 267. The optimal distance L between the reflectingplate and the opposite substrate can be determined by the followingequation:L=λ/4+(n−1)λ/2(n=1,2,3, . . . )

And ultraviolet rays or visible rays are then irradiated on the uppersubstrate 320 to cure the sealant 330. The optimal range for wavelengthused to cure the sealant is from 200 nm to 700 nm. Another designconsideration is that it is preferable to have at least 25% of the totalsurface area of the sealant 330 in contact with reflecting plate 267. Asdiscussed earlier, it is preferable to form the reflecting plate 267 andthe source/drain electrodes 261 and 265 at the same time to reduce thenumber of processing steps and to reduce manufacturing costs in thefourth embodiment. Alternatively, the reflecting plate 267 can bedeposited and patterned at the same time as when the gate electrode 240is formed. Alternatively, the reflecting plate 267 can be formed at thebeginning of the process, before buffer layer 210 is formed on lowerinsulating substrate 200. Before forming the buffer layer 210, amaterial having good reflectivity, such as any one metal of Al, Mo, Ti,Ag and Mg, or an alloy containing at least one of these metals (i.e.,Mo/Al/Mo, Ti/Al/Ti) may be deposited and patterned on the lowerinsulating substrate 200 to form the reflecting plate 267 in theencapsulating junction region of the display.

In another design consideration, the width of the reflecting plate 267in FIG. 8 is illustrated to be larger than the contact area of thesealant 330, however, the width of the reflecting plate 267 may beformed to be smaller than the contact area contact area of the sealant330. In such a scenario, the sealant 330 may contact lower insulatingsubstrate 200.

The inclusion of the reflecting plate 267 in the design of the electroluminescent display attached to a light-cured sealant 330 in the edge orencapsulation junction region is advantageous for the following reason.Light used to cure the sealant 330 also exposes other portions of theelectro luminescent display. This light used to cure the sealant 330 candamage other parts of the electro luminescent display. By placing areflective plate in the encapsulation junction region of the display,less incident light energy is needed to cure the sealant because boththe incident light and the reflected light can be used to cure thesealant. Therefore, the intensity of the incident light needed to curethe sealant is less if the reflecting plate is present. Therefore,because less incident light is needed to cure the sealant, less damageis sustained by the electro luminescent display during the curingprocess.

Turning now to FIGS. 9 and 10, FIGS. 9 and 10 illustrate top views ofelectro luminescent displays according to the fourth embodiment of thepresent invention. As is clearly illustrated in FIGS. 9 and 10, thewidth of the sealant 330 is greater than the width of the reflectingplate 267. Therefore, in the designs illustrated in FIGS. 9 and 10, thesealant 330 maybe in contact with lower insulating substrate 200.

In FIG. 9, the reflecting plate 267 is formed as one continuous piece inthe form of a closed square. Alternatively, in FIG. 10, the reflectingplate 267 is formed of four discrete portions disconnected from eachother. It is to be appreciated that the reflecting plate 267 does notserve to conduct electricity, and thus having four discrete segments inFIG. 10 works just as well as one continuous closed piece in FIG. 9.

Fifth Embodiment

FIG. 11 is a cross-sectional view showing the encapsulating junctionregion of the organic electro luminescent display in accordance with afifth embodiment of the invention. The organic electro luminescentdisplay according to the fifth embodiment has a similar structure asthat of the fourth embodiment except the location of the reflectingplate 267. The reflecting plate 267 in the fifth embodiment of thepresent invention is in an inside surface of upper substrate 320 insteadof being on the inside surface of lower insulating substrate 200. Inorder to form the structure of FIG. 11, after forming the TFT and thelight emitting element LE on the lower insulating substrate 200 asillustrated in FIG. 7, a metal thin layer is then deposited andpatterned on the inner side of the upper substrate 320 to form thereflecting plate 267 in the encapsulating junction region. As in thefourth embodiment, the upper substrate 320 is bonded to the lowerinsulating substrate 200 by using the sealant 330 in the encapsulatingjunction region.

Sixth Embodiment

FIG. 12 is a cross sectional view showing an encapsulating junctionregion of the organic electro luminescent display in accordance with asixth embodiment of the invention. The organic electro luminescentdisplay according to the sixth embodiment has a similar structure asthat of the fourth and fifth embodiments except for the location of thereflecting plate 267. In the sixth embodiment, the reflecting plate 267is located on the outer side of lower insulating plate 200. In the sixthembodiment as in the fourth and the fifth embodiments, the reflectingplate is located only in the encapsulated junction region at the edgesof the electro luminescent display.

In order to make the structure of FIG. 12, after forming the TFT and thelight emitting element on the lower insulating substrate 200 asillustrated in FIG. 7, the upper substrate 320 is bonded to the lowerinsulating substrate 200 by using the sealant 330 in the encapsulatingjunction region. After encapsulating the upper substrate 320 to thelower insulating substrate 200, a metal thin layer is deposited andpatterned on an outer side of the lower insulating substrate 200 to formthe reflecting plate 267 in the encapsulating junction region.

Seventh Embodiment

FIG. 13 is a cross sectional view showing an encapsulating junctionregion of the organic electro luminescent display in accordance with aseventh embodiment of the invention. The organic electro luminescentdisplay according to the seventh embodiment has a similar structure asthat of the fourth embodiment but that the reflecting plate 267 isformed on an outer side of the upper insulating plate 320 as opposed toan inner side of lower insulating substrate 200.

In order to form the structure of FIG. 13, after forming the TFT and thelight emitting element on the lower insulating substrate 200 asillustrated in FIG. 7, a thin metal layer is deposited and patterned onthe outer side of the upper substrate 320 to form the reflecting plate267 in the encapsulating junction region. After forming the reflectingplate 267 in the encapsulating junction region on the outer side of theupper substrate 320, the upper substrate 320 is then bonded to the lowerinsulating substrate 200 by using the sealant 330 in the encapsulatingjunction region.

Eighth Embodiment

FIG. 14A and FIG. 14B are a cross sectional view showing anencapsulating junction region of the organic electro luminescent displayin accordance with an eighth embodiment of the invention. The organicelectro luminescent display according to the eighth embodiment has asimilar structure as that of the fourth embodiment except that awaveguide 217 is formed on the inner side of lower insulating substrateinstead of the reflecting plate 267. Preferably the wave guide isunevenness or a convex lens. FIG. 14A illustrates the wave guide 217 asunevenness. FIG. 14B illustrates wave guide 217 as a convex lens.

Referring to FIG. 14A and FIG. 14B, the wave guide 217 of the organicelectro luminescent display according to the eighth embodiment is formedon the inner side of the encapsulating junction region of the lowerinsulating substrate 200 during the process of forming the TFT havingthe structure illustrated in FIG. 7 in the pixel portion. Afterdepositing and patterning the buffer layer 210, the wave guide 217 isformed in a position corresponding to the encapsulating junction regionof the lower insulating substrate 200.

Alternatively, the wave guide 217 may be formed simultaneous to thepatterning the gate insulating layer 230 and after depositing the gateinsulating layer 230. Alternatively, wave guide 217 can be formedsimultaneous to the etching of the interlayer insulating layer 250 toform the contact holes 251 and 255. Alternatively, the wave guide 217may be formed simultaneous to the etching of the passivation layer 270to form the via-hole 275.

Another alternative is to form a multi-layered wave guide 217 that isformed simultaneous to the formation of the buffer layer 210, gateinsulating layer 230, interlayer insulating layer 250, and passivationlayer 270. Alternatively, wave guide 217 made out of material having theoptical transmissivity may be formed in a separate process step separatefrom the process of forming the other layers in FIG. 7.

The wave guide 217 is formed by adjusting an angle in consideration of arefraction index of the incident light, and makes the incident lightfocused on the sealant 330 of the encapsulating junction region to beformed later by the refraction.

Ninth Embodiment

FIG. 15A and FIG. 15B are a cross-sectional view showing anencapsulating junction region of the organic electro luminescent displayin accordance with a ninth embodiment of the invention. The organicelectro luminescent display according to the ninth embodiment has thesame structure in the pixel portion as that of the eighth embodimentexcept that the wave guide 217 is formed on an inner surface of theupper substrate 320 instead of on the inner surface of the lowerinsulating substrate. FIG. 15A illustrates wave guide 217 as unevennessand FIG. 15B illustrates wave guide 217 as a convex lens.

The method of forming the structure if FIG. 15A and FIG. 15B is asfollows. After forming the TFT and the light emitting element on thelower insulating substrate 200, a material having optical transmissivityis deposited on the inner side of the upper substrate 320. The materialhaving the optical transmissivity is then patterned to form the waveguide 217 on the inner of the upper substrate 320 in the encapsulationjunction region. After forming the wave guide 217 on the inner side ofthe encapsulating junction region in the upper substrate 320, the lowerelectrode 280, the organic layer 300, and the upper electrode 310 arethen formed on the upper substrate 320.

Tenth Embodiment

FIG. 16A and FIG. 16B are a cross-sectional view illustrating anencapsulating junction region of the organic electro luminescent displayin accordance with a tenth embodiment of the invention. The organicelectro luminescent display according to the tenth embodiment has theTFT and the light emitting element shown in FIG. 7 in the pixel portion,and has two wave guides 217, one formed on the inner surface of theupper substrate 320 and one formed on the inner surface of the lowerinsulating substrate 200. FIG. 16A illustrates wave guide 217 asunevenness while FIG. 16B illustrates wave guide 217 as a convex lens.

The wave guide 217 is formed on the inner side lower insulatingsubstrate 200 is formed according to the same processes as thatdescribed in the eighth embodiment of FIG. 14A and FIG. 14B. The waveguide 217 formed on the inner side upper substrate 320 is made accordingto a process described in the formation of the wave guide 217 in thediscussion of FIGS. 15A and 15B (the ninth embodiment). That is, thelower electrode 280, the organic layer 300, and the upper electrode 310are then formed on an inner surface of upper substrate 320 afterwaveguide 217 is formed in the inner surface of upper substrate 320.

In addition, in the above-mentioned embodiments of the invention, anorganic electro luminescent display having enhanced curing efficiency isdisclosed by using both a reflecting plate and a wave guide formed inthe upper substrate 320 or the lower insulating substrate 200 eitherrespectively or anti respectively. Alternatively, two reflecting platesmay be used, one attached to a surface of the upper substrate 320 andone attached to a surface of lower insulating substrate 200. Thereflecting plates formed on both sides of the organic electroluminescent display are preferably formed to have a mirror attached to.

According to the invention, auxiliary layers are formed to removeorganic layers on the encapsulating junction region, so that theinvention can provide an organic electro luminescent display capable ofeasily removing the organic layers formed on the encapsulating junctionregion during the process of forming organic layers. In addition, theinvention can provide a method for fabricating the organic electroluminescent display with reduced damage in the pixel portion by removingthe organic layers disposed on auxiliary layers by a laser instead ofremoving the organic layers directly formed on the substrate.

Furthermore, according to the invention, a reflecting plate is disposedin the encapsulating junction region, so that the light emitted from thelight source is reflected by the reflecting plate for curing thesealant, thereby enhancing the curing state of the sealant and puttingthe encapsulation of the substrates in better condition. In addition,with the reflective plate, the curing time is reduced, resulting in lessdamage sustained in the pixel regions of the display.

While the invention has been described with reference to a particularembodiment, it is understood that the disclosure has been made forpurpose of illustrating the invention by way of examples and is notlimited to limit the scope of the invention. And one skilled in the artcan make amend and change the invention without departing from the scopeand spirit of the invention.

1-15. (canceled)
 16. An organic electro luminescent display, comprising:a lower insulating substrate on which TFTs and light emitting elementsare formed; an upper substrate attached to the lower insulatingsubstrate; an encapsulating junction region adapted to encapsulate andattach the upper substrate to the lower insulating substrate via asealant; and a reflecting plate arranged in the encapsulating junctionregion at any one side of the upper substrate and the lower insulatingsubstrate.
 17. The display of claim 16, the reflecting plate beingformed on an inner side of one of the upper substrate and the lowerinsulating substrate, the reflecting plate facing the other of the uppersubstrate and the lower insulating substrate.
 18. The display of claim16, the reflecting plate being formed on an outer side of one of theupper substrate and the lower insulating substrate.
 19. The display ofclaim 16, the sealant being an optical curing sealant.
 20. The displayof claim 19, the sealant being an optical curable sealant cured byexposure to light in either a visible ray range or an ultraviolet rayrange.
 21. The display of claim 16, the reflecting plate comprising ametal thin layer deposited on any one side of the upper substrate andthe lower insulating substrate.
 22. The display of claim 16, thereflecting plate comprising a mirror attached to the outer side of oneof the upper substrate and the lower insulating substrate.
 23. Thedisplay of claim 16, wherein a distance from the reflecting plate to anearest surface of a substrate opposing the reflecting plate is designedso that curing light reflected off the reflective plate constructivelyinterferes with curing light incident to the reflective plate.
 24. Anorganic electro luminescent display, comprising: a lower insulatingsubstrate on which TFTs and light emitting elements are formed; an uppersubstrate bound to the lower insulating substrate; an encapsulatingjunction region adapted to encapsulate the upper substrate to the lowerinsulating substrate via a sealant; and a wave guide arranged in theencapsulating junction region on an inner side of one or both of theupper substrate and the lower insulating substrate.
 25. The display ofclaim 24, wherein the wave guide is unevenness.
 26. The display of claim24, wherein the wave guide is a convex lens.
 27. The display of claim24, wherein the wave guide is formed on both the upper substrate and thelower insulating substrate.
 28. The display of claim 24, wherein theencapsulating junction region being separate from where the TFTs and thelight emitting elements are arranged.
 29. The display of claim 24,wherein the wave guide is comprised of a material with opticaltransmissive property.
 30. The display of claim 29, wherein the waveguide is comprised of a material selected from the group consisting ofSiO₂ and SiN_(x).
 31. An organic electro luminescent display,comprising: a lower insulating substrate on which a pixel portion isarranged; an upper substrate arranged over the lower insulatingsubstrate; and a sealing material arranged between the upper substrateand the lower insulating substrate and adapted to seal the uppersubstrate to the lower insulating substrate, wherein a metal layer isarranged between the lower insulating substrate and the sealingmaterial.
 32. The display of claim 31, wherein the sealing material isformed along the peripheries of the substrates and not in the pixelportion of the display.
 33. The display of claim 32, wherein the metallayer is formed coextensively along with the sealing material and is ofthe shape of a closed polygon.
 34. The display of claim 32, wherein themetal layer is formed discontinuously in separate unconnected piecesaround a perimeter of the display and along the sealing material. 35.The display of claim 31, the metal layer comprising a material beingselected from the group consisting of Al, Mo, Ti, Ag, Mg and an alloycontaining at least one of Al, Mo, Ti, Ag and Mg.
 36. The display ofclaim 31, wherein at least 25% of the total surface area of the sealingmaterial is in contact with said metal layer.
 37. An organic electroluminescent display, comprising: a lower insulating substrate on which apixel portion is formed; an upper substrate arranged on the lowerinsulating substrate; and a sealing material arranged between the uppersubstrate and the lower insulating substrate, the sealing material beingadapted to attach the upper substrate to the lower insulating substrate;and a reflecting plate arranged between the lower insulating substrateand the sealing material.
 38. The display of claim 37, the sealingmaterial being arranged along peripheries of the substrates and outsideof the pixel portion.
 39. The display of claim 38, wherein thereflecting plate is arranged to be coextensive with the sealing materialand is in the shape of a closed polygon.
 40. The display of claim 38,the reflecting plate being a plurality of separate unconnected segmentsarranged essentially along the sealing material.
 41. The display ofclaim 37, wherein at least 25% of an outer surface of the sealingmaterial is in contact with the reflecting plate.
 42. The display ofclaim 37, the reflecting plate being comprised of metal.
 43. The displayof claim 42, the metal being selected from a group consisting of Al, Mo,Ti, Ag, Mg and an alloy containing at least one metal of Al, Mo, Ti, Agand Mg.
 44. An organic electro luminescent display, comprising: a lowerinsulating substrate on which TFTs and light emitting elements areformed; an upper substrate bound to the lower insulating substrate; anencapsulating junction region surrounding and outside of the TFTs andlight emitting elements, the encapsulating junction region adapted toattach the upper substrate to the lower insulating substrate via asealant; and an auxiliary layer disposed in the encapsulating junctionregion of the display.
 45. The display of claim 44, wherein theauxiliary layer is arranged on a layer being selected from the groupconsisting of the upper substrate and the lower insulating substrate.46. The display of claim 44, wherein the auxiliary layer is arranged onan outer side of one of the upper substrate and the lower insulatingsubstrate.
 47. The display of claim 44, wherein the auxiliary layers arereflecting plates.
 48. The organic electro luminescent display accordingto claim 44, wherein the auxiliary layers are adapted to aid in removalby laser of organic layers deposited on the auxiliary layers.